What do you mean by; inaccessible ? If clearing cookies didn't help then it is possible that the '''cookies.sqlite''' file that stores the cookies got corrupted. Rename (or delete) cookies.sqlite (cookies.sqlite.old) and delete other present cookies files like '''cookies.sqlite-journal''' in the Firefox profile folder in case the file cookies.sqlite got corrupted. http://kb.mozillazine.org/Cookies https://support.mozilla.org/kb/Deleting+cookies Type '''about:support'''<enter> in the address bar. Under the page logo on the left side, you will see '''Application Basics. ''' Under this find '''Profile Folder. ''' To its right press the button '''Show Folder. ''' This will open your file browser to the current Firefox profile. Now '''Close Firefox. ''' Locate the above file. Then rename or delete it. Restart Firefox.

See also Options/Preferences -> Privacy & Security. *https://support.mozilla.org/en-US/kb/firefox-options-preferences-and-settings